package cn.kingshion.reflectiong;

import java.lang.annotation.*;
import java.lang.reflect.Field;

/**
 * 反射操作注解
 */
public class Test09 {
    public static void main(String[] args) throws ClassNotFoundException, NoSuchFieldException, IllegalAccessException {
        Class c1 = Class.forName("cn.kingshion.reflectiong.Student");

        // 通过反射获得注解
        Annotation[] annotations = c1.getAnnotations();
        for (Annotation annotation : annotations) {
            System.out.println(annotation);
        }

        // 获得注解的 value 值
        TableStu tableStu = (TableStu) c1.getAnnotation(TableStu.class);
        String value = tableStu.value();
        System.out.println(value);

        // 获得类指定的注解
        Field field = c1.getDeclaredField("name");
        FieldStu annotation = field.getAnnotation(FieldStu.class);
        System.out.println(annotation.columnName());
        System.out.println(annotation.type());
        System.out.println(annotation.length());
    }
}


/**
 * 数据库的映射
 */
@TableStu("db_student")
class Student {
    @FieldStu(columnName = "db_id", type = "int", length = 10)
    private int id;

    @FieldStu(columnName = "db_age", type = "int", length = 10)
    private int age;

    @FieldStu(columnName = "db_name", type = "varchar", length = 3)
    private String name;

    public Student() {
    }

    public Student(int id, int age, String name) {
        this.id = id;
        this.age = age;
        this.name = name;
    }

    @Override
    public String toString() {
        return "Student{" +
                "id=" + id +
                ", age=" + age +
                ", name='" + name + '\'' +
                '}';
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }
}

// 类名注解
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@interface TableStu {
    String value();
}

// 字段的注解
@Target(ElementType.FIELD)
@Retention(RetentionPolicy.RUNTIME)
@interface FieldStu {
    String columnName();

    String type();

    int length();
}